1. Field of the Invention
The invention relates to a device for spatial location and destruction of concretions in bodily cavities by application of ultrasonic shock waves which are generated in pulsed manner by a focussing shockwave transducer having its focus adjustable on the concretion in question. The transducer may, if applicable, be operated at reduced power according to the pulse echo principle as an A-scanner during the locating operation, whereas it is possible by means of at least one B-scanner to generate a B-section picture of the body tissue traversed by the ultrasonic field of a monitor, so that by means of a relative displacement between the patient and the device, the concretion depicted in the section picture may be placed in coincidence with a target mark present on the monitor and indicating the position of the transducer focus, and the shock wave transducer may subsequently be placed in operation for the purpose of destroying the concretion with the sonic pressure waves generated during the locating and destruction operations being transmitted to the patient's body via a coupling fluid.
2. Description of the Prior Art
Devices of this kind have proved themselves in the location and destruction of concretions, such as kidney, bladder and gall stones, primarily because as compared to surgical intervention, their application is less dangerous to the patient in view of the contactless destruction of the concretion in question. Difference in the function and application of the known devices derive in essence from the nature of the shock wave generation.
Various arrangements are known for providing the required coupling between a shock wave transducer and the patient. Examples are disclosed in U.S. Pat. No. 4,526,168, whose disclosure is incorporated by reference thereto and which was based on German application No. 3119295; in U.S. Pat. No. 3,237,623; in German applications Nos. 2913251 and 3220751; and in copending U.S. patent application Ser. No. 614,145, which was filed May 25, 1984 and is based on German application No. 3319871.
There are devices disclosed for example in U.S. Pat. No. 3,942,531 which claimed priority from German application 2351247 and German patent specifications Nos. 2718847; 2722252; 2913251; 3122056 and 3220751 in which the shock waves are generated by spark discharge at a focus of a partially eliptical focussing chamber and the other focus may be placed in coincidence with the concretion which is to be destroyed, by adjustment of the device. Relatively high striking voltages are required for spark discharges, as known, so that problems arise in the provision of suitable electrical insulation for the patient, which are costly to resolve. Furthermore, spark discharges lead to burn-off of the electrodes, so that a commensurate maintenance cost will occur.
Ultrasonic transducers will be more satisfactory in this connection, if they comprise one or more commonly, several ceramic elements and are operated by voltage in a pulsed manner, for example, in water as a coupling fluid with respect to the patient. Transducers of this nature, which are disclosed for example in U.S. patent application Ser. No. 614,145, German patent application No. 654673, the above mentioned U.S. Pat. No. 4,526,168 and U.S. Pat. No. 4,607,931, whose disclosure is incorporated by reference and claims priority from the same French application as EP specification No. 148653, are advantageous, in particular because of their durability and risk-free application. Focussing transducers may also be produced in comparatively uncomplicated manner, by mosaic-like positioning of individual transducer elements on a support in the shape of a spheroidal cap or cup, for example. On the other hand, an electronic focussing action is also possible in the case of such transducers assembled from several transducer elements, by appropriate chronologically staged actuation of the transducer elements.
A special problem arises however in these devices in connection with the location of the concretion and the alignment of the focus of the shock wave transducer on the concretion. In this connection, an adjustment under X-ray observation is not advisable in view of the patient's radiation exposure. For this reason, the method has already been adapted to generate sectional pictures of the organ or body area in question by means of B-scanners and to adjust the focus of the shock wave transducer with respect to the concretion under observation of the section pictures on monitors. If, for example, two scanners arranged at an angle of 90.degree. with respect to each other are utilized, the concretions may be clearly depicted on the monitor in two sectioning planes and the focus may if applicable still be adjusted in another plane relative to the concretion by displacement of the shock wave transducer.
It will frequently be sufficient however if the position of the focus is indicated on the monitor by means of a target mark, and if the concretion displayed on the monitor by means of the sectional pictures is placed in coincidence with the target mark by displacement of the device or variation of the patient's position. The shock wave transducer may furthermore also be involved in the locating operation, by allowing it to operate at comparatively low power as an A-scanner in a transceiver mode or rather according to the pulse echo principle. It is possible upon occurrence of a typical maximum of the echo signals being equally displayed on the monitor, to determine whether the transducer focus will be situated within or on the concretion.